Southwestern American Indians have lower serum cholesterol levels and lower prevalence of atherosclerosis than Caucasian control groups. To characterize these differences, we are investigating the lipoprotein cholesterol content and the kinetics of radiolabelled autologous low density lipoprotein in Southwestern American Indians and controls. The results of this study will elucidate the mechanisms responsible for the low LDL levels in this population and their relation to atherosclerosis.